Several publications and patent documents are referenced in this application in order to describe more fully the state of the art to which this invention pertains. The disclosure of each of these publications is incorporated herein by reference.
Lateral flow assay devices and methods are known in the art. Previously such devices have been developed to test samples that are easily available in large quantities. Generally such devices comprise a lateral flow matrix, such as a nitrocellulose matrix for example, to which a fluid sample is applied. Fluid within the sample travels along the matrix and one or more analytes within the sample react with reagents contained within the lateral flow matrix. Typically at least one of these reagents is immobilised within the matrix allowing any reaction with the analytes to be detected at a specific area of the matrix, for example, by visual inspection.
When the test sample is blood, or a component of blood, collection of a large sample is not always possible or convenient, for example at a point-of-care such as a pharmacy or a doctor's surgery. In addition, lateral flow devices are generally unsuitable for small fluid samples, such as for analysis of ‘finger prick’ volumes of blood. In this case the membrane may dry before the assay is completed or there may be insufficient fluid to travel the length of the test device before measurement is possible. Also, as the scale of devices in which fluids are manipulated is decreased, there exists the significant disadvantage that there is a tendency for such fluids to maintain a stable laminar flow. This makes efficient mixing of liquids and, for example, reagents difficult limiting the extent to which assay devices may be successfully reduced in scale without increasing the complexity of the device. FIG. 1 provides examples from the art of existing, complex, assay devices.
As such, a need currently exists for simple and efficient devices that allow rapid testing whilst enabling lower or smaller volumes of a sample to be analysed. One area where such devices would be useful is in the field of cholesterol and blood lipid testing.